Cooling device

ABSTRACT

[Problem] When a size of a cooling device using a boiling cooling system is reduced, a cooling performance decreases. 
     [Means for solving the problems] It is characterized in that an evaporation unit which stores refrigerant, a condensing unit which condenses a gas-phase refrigerant produced by vaporizing the refrigerant in the evaporation unit to a liquid and dissipates heat, a vapor pipe which conveys the gas-phase refrigerant to the condensing unit, and a liquid pipe which conveys a liquid-phase refrigerant obtained by condensing the gas-phase refrigerant in the condensing unit to the evaporation unit are included, the condensing unit includes a heat dissipation flow path, an upper header which connects the vapor pipe and the heat dissipation flow path, and a lower header which connects the heat dissipation flow path and the liquid pipe, the upper header includes a flow path header portion connected to the heat dissipation flow path and an upper header extension portion located around the flow path header portion, and the upper header extension portion has a connection port connected to the vapor pipe in a face to which the heat dissipation flow path is connected.

TECHNICAL FIELD

The present invention relates to a cooling device and in particular,relates to a cooling device using a phase change of a refrigerant.

BACKGROUND ART

In recent years, in order to improve a processing speed of an electronicequipment, a plurality of central processing units (CPUs) are mounted ona circuit board.

The circuit board is installed in an electronic device with a hard diskdevice or the like in high density.

Generally, when a temperature of a semiconductor device such as a CPU orthe like exceeds a predetermined temperature, not only the performanceof the semiconductor device cannot be maintained but also thesemiconductor device is destroyed in some cases. For this reason, atemperature control using cooling or the like is required and atechnology by which the semiconductor device in which the amount of heatgenerated increases can be efficiently cooled is strongly desired.

Accordingly, a study of the boiling cooling system in which the coolingis performed by using a phase change of a refrigerant is performed. Inthe boiling cooling system, the refrigerant is boiled by the heatgenerated by a heating element in an evaporation unit and the vapor ofthe refrigerant is sent to a condensing unit. Whereby, the heat isconveyed and the cooling is performed.

When described in detail, the vapor of the refrigerant that is producedby vaporizing the refrigerant by the heat of the heating element in theevaporation unit is circulated by using the buoyancy due to the densitydifference between a gas and a liquid and sent to the condensing unit.When the refrigerant is cooled by the heat exchange with the outside airin the condensing unit, the vapor of the refrigerant (gas-phaserefrigerant) is condensed to a liquid and the heat generated by theheating element is dissipated to the outside. Further, the refrigerantobtained by condensing the gas-phase refrigerant flows back to theevaporation unit by gravity.

A cooling system mounted on an electronic circuit board is described inpatent document 1. The above-mentioned cooling system includes a heatreceiving jacket which vaporizes the liquid refrigerant by the heatgenerated by a semiconductor device, a condenser which condenses therefrigerant vapor to a liquid by conducting the heat to the outside, afirst pipe (a vapor pipe) which conveys the refrigerant vapor to thecondenser from the heat receiving jacket, and a second pipe (a liquidreturn pipe) which conveys the liquid refrigerant to the heat receivingjacket from the condenser. Further, the condenser includes a pair ofheaders and a plurality of flow paths having a flat shape between thepair of headers. The vapor pipe and the liquid return pipe aresandwiched between the pair of headers of the condenser and connected toeach other.

By using the above-mentioned structure, the refrigerant is circulated inthe cooling system by using the phase change in which the refrigerant isvaporized by the heat of the semiconductor device. The vapor of therefrigerant which is conveyed to an upper part of the condenserextending in a vertical direction is condensed to the liquid refrigerantby the heat exchange with the outside. The liquid refrigerant flows to alower part of the condenser and flows back to the heat receiving jacket.

PRIOR ART DOCUMENT Patent Document

[patent document 1] Japanese Patent Application Laid-Open No. 2011-47616

BRIEF SUMMARY OF THE INVENTION Problems to be Solved by the Invention

With the increase of the amount of heat generation of the semiconductordevice such as a CPU or the like, as an alternative of a heat sink, arequest for mounting the cooling device using the boiling cooling systemin the electronic equipment such as a server or the like increases. Whenthe cooling device using the boiling cooling system is mounted in theelectronic equipment such as the server or the like, with the decreasein size of the electronic equipment, it is necessary to reduce theheight of the cooling device using the boiling cooling system anddispose the condensing unit near a heat receiving unit.

However, in the cooling device described in patent document 1, becausethe vapor pipe is connected to a side surface part of the header of thecondenser, it is required that the thickness of the header is greaterthan the outer diameter of the vapor pipe. In other words, because theminimum thickness of the header is limited, when the height of thecooling device is reduced, the length of a flat pipe for dissipatingheat has to be shortened. Therefore, a problem in which a coolingperformance decreases occurs.

Further, when the evaporation unit and the condensing unit are closelydisposed to reduce the size of the cooling device, the curvature of thevapor pipe becomes large and whereby it becomes difficult to achieve abending work. Therefore, a problem in which a manufacturing accuracy isreduced and a cost increases occurs. On the other hand, when the narrowvapor pipe is used, a problem in which the internal pressure of therefrigerant increases and whereby the cooling performance decreasesoccurs.

Thus, when the size of the cooling device described in patent document 1is reduced, a problem in which the cooling performance decreases occurs.

An object of the present invention is to provide a cooling device whichcan solve the above-mentioned problem in which the cooling performancedecreases when the size of the cooling device is reduced.

Means for Solving the Problems

It is characterized in that an evaporation unit which stores arefrigerant, a condensing unit which condenses a gas-phase refrigerantproduced by vaporizing the refrigerant in the evaporation unit to aliquid and dissipates heat, a vapor pipe which conveys the gas-phaserefrigerant to the condensing unit, and a liquid pipe which conveys aliquid-phase refrigerant obtained by condensing the gas-phaserefrigerant in the condensing unit to the evaporation unit are included,the condensing unit includes a heat dissipation flow path, an upperheader which connects the vapor pipe and the heat dissipation flow path,and a lower header which connects the heat dissipation flow path and theliquid pipe, the upper header includes a flow path header portionconnected to the heat dissipation flow path and an upper headerextension portion located around the flow path header portion, and theupper header extension portion has a connection port for connecting tothe vapor pipe in a face to which the heat dissipation flow path isconnected.

Effect of the Invention

By the cooling device of the present invention, the cooling device usingthe boiling cooling system which has a sufficient cooling performanceeven when the size of the cooling device is reduced can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing a structure of a cooling deviceaccording to a first exemplary embodiment of the present invention.

FIG. 2 is a perspective view showing a structure of a cooling deviceaccording to a second exemplary embodiment of the present invention.

FIG. 3 is a schematic view for explaining action of a cooling deviceaccording to a second exemplary embodiment of the present invention.

FIG. 4 is a perspective view showing a structure of a cooling deviceaccording to a third exemplary embodiment of the present invention.

FIG. 5 is a perspective view showing a structure of a cooling deviceaccording to a third exemplary embodiment of the present invention.

FIG. 6 is a perspective view showing a structure of a cooling deviceaccording to a fourth exemplary embodiment of the present invention.

MODE FOR CARRYING OUT THE INVENTION

A preferred mode for carrying out the present invention will bedescribed below by using a drawing. In the exemplary embodimentdescribed below, a technically desirable limitation is included to carryout the present invention. However, this does not limit the scope of theinvention.

First Exemplary Embodiment

First, this exemplary embodiment will be described in detail withreference to the drawing. FIG. 1 is a perspective view showing astructure of a cooling device 10 according to this exemplary embodiment.

Explanation of the Structure

As shown in FIG. 1, the cooling device 10 according to this exemplaryembodiment includes an evaporation unit 1, a condensing unit 2, a vaporpipe 3, and a liquid pipe 4.

The evaporation unit 1 has an enclosed structure and stores arefrigerant therein. In the cooling device 10, the air is exhausted by apump or the like and an internal pressure is equal to a saturated vaporpressure of the refrigerant. In this exemplary embodiment, specifically,HFC (hydro fluorocarbon) or HFE (hydro fluor ether) is used for therefrigerant. However, it is not limited to these fluids. Further, theevaporation unit 1 is set so that a lower surface part of theevaporation unit 1 is thermally connected to the heating element andused. The refrigerant receives heat generated by the heating element andboils.

The heating element is an element which generates heat when it operates.For example, it is a CPU or the like. It is not limited in particular.Further, although the heating element is not shown in a figure, it maybe mounted on a substrate. It is desirable that the surface of theheating element which contacts with the evaporation unit 1 is thermallyconnected to the evaporation unit 1 through a resin having high thermalconductivity or the like such as a heat conduction grease or the like.

The condensing unit 2 is composed of an upper header 5, a lower header6, and a heat dissipation flow path 7.

The heat dissipation flow path 7 has a shape extending in a verticaldirection. An upper end part of the heat dissipation flow path 7 isconnected to the upper header 5 and a lower end part thereof isconnected to the lower header 6.

The heat dissipation flow path 7 has a hollow tube shape and therefrigerant flows in an internal space. Further, it is desirable thatthe heat dissipation flow path 7 has a flat shape. However, the shape isnot limited to this shape. Further, a material having high thermalconductivity such as copper, aluminum, or the like can be used for thematerial of the heat dissipation flow path 7. The material is notlimited in particular.

The vapor pipe 3 connects an upper part of the evaporation unit 1 andthe upper header 5 and conveys the vapor of the refrigerant (gas-phaserefrigerant) that is produced by vaporizing the refrigerant in theevaporation unit 1 to the heat dissipation flow path 7 via the upperheader 5.

The liquid pipe 4 connects the lower header 6 and a lower part or a sidesurface part of the evaporation unit 1 and conveys the liquefiedrefrigerant (liquid-phase refrigerant) obtained by condensing thegas-phase refrigerant in the condensing unit 2 to the evaporation unit1.

Further, the vapor pipe 3 and the liquid pipe 4 may have a bilayerstructure in which an inner layer is a metal layer and an outer layer isa resin layer or a single layer structure in which an inner layer is ametal layer and an outer layer is a metal layer.

The upper header 5 is composed of a flow path header portion 5 aconnected to the heat dissipation flow path 7 and an upper headerextension portion 5 b located around the flow path header portion 5 a.The lower surface part of the flow path header portion 5 a is connectedto the heat dissipation flow path 7. Further, a connection port 20connected to the vapor pipe 3 is provided in the lower surface part ofthe upper header extension portion 5 b. Namely, the lower surface partof the upper header 5 composed of the flow path header portion 5 a andthe upper header extension portion 5 b is connected to the vapor pipe 3and the heat dissipation flow path 7.

In other words, the lower surface part of the upper header 5 connectsthe vapor pipe 3 and the heat dissipation flow path 7. Whereby, theupper header 5 conveys the vapor of the refrigerant (gas-phaserefrigerant) that is conveyed by the vapor pipe 3 to the heatdissipation flow path 7. Further, an area of the lower surface part ofthe upper header 5 is determined so as to be greater than across-sectional area perpendicular to the vertical direction of the heatdissipation flow path 7 by at least an area of the upper headerextension portion 5 b.

Further, the vapor pipe 3 connects the upper part of the evaporationunit 1 and the lower surface part of the upper header 5. Therefore, asshown in FIG. 1, a pipe having a shape extending in a straight lineshape can be used for the vapor pipe 3. Therefore, a bending work or thelike is not required to produce it.

In FIG. 1, an upper surface part of the lower header 6 is connected tothe heat dissipation flow path 7 and a side surface part thereof isconnected to the liquid pipe 4. However, the connection relationship ofthe lower header 6 is not limited in particular. When the vapor of therefrigerant flows in the heat dissipation flow path 7, the vapor of therefrigerant is condensed to the liquid. The lower header 6 collects theliquefied refrigerant (liquid-phase refrigerant). The liquefiedrefrigerant (liquid-phase refrigerant) flows back to the evaporationunit 1 through the liquid pipe 4.

Explanation of the Action and Effect

Next, the action and effect of this exemplary embodiment will bedescribed.

The evaporation unit 1 is made of a material having high thermalconductivity and thermally connected to the heating element through aheat conduction grease or the like. Therefore, the heat generated by theheating element is conducted to the refrigerant provided inside theevaporation unit 1 through the evaporation unit 1.

The refrigerant receives the heat generated by the heating element andboils. The vapor of the refrigerant (gas-phase refrigerant) that isgenerated when the refrigerant provided in a closed space of theevaporation unit 1 boils flows to the upper header 5 through the vaporpipe 3 by buoyancy due to the density difference between the gas and theliquid.

The vapor of the refrigerant (gas-phase refrigerant) that is conveyed tothe upper header 5 flows the heat dissipation flow path 7 and whereby,the heat exchange with the outside air is performed. When the heatdissipation flow path 7 is cooled, the vapor of the refrigerant(gas-phase refrigerant) that flows inside the heat dissipation flow path7 is cooled and condensed to a liquid. The liquefied refrigerant(liquid-phase refrigerant) falls to the lower part of the heatdissipation flow path 7 by the gravity and flows back to the evaporationunit 1 through the liquid pipe 4. The refrigerant boils by the heatgenerated by the heating element in the evaporation unit 1 again and acooling cycle is repeated.

Thus, the refrigerant provided inside the evaporation unit 1 changesfrom the liquid to the gas by the heat generated by the heating elementand when it flows in the heat dissipation flow path 7, it is cooled andthe gas is condensed to the liquid again. Namely, the phase of therefrigerant is repeatedly changed from the liquid phase to the gas phaseand from the gas phase to the liquid phase and whereby, the heatgenerated by the heating element is dissipated through the heatdissipation flow path 7.

When an amount of heat generation that is generated by the heatingelement is large, in order to cool the heating element, much refrigerantis required. However, when the liquid vaporizes, its volume increases bymore than several hundred times. Therefore, when the refrigerant boilsand vaporizes by the heat generated by the heating element, the internalpressure of the evaporation unit 1 and the vapor pipe 3 in which thevapor of the refrigerant (gas-phase refrigerant) flows increases.

When the internal pressure of the evaporation unit 1 increases, not onlythe evaporation unit 1 deforms but also a problem in which a coolingperformance decreases occurs because the boiling point of therefrigerant increases. Accordingly, in this exemplary embodiment, thecross-sectional area of the vapor pipe 3 is made greater than that ofthe liquid pipe 4 and the volume of the evaporation unit 1 and thevolume of the vapor pipe 3 are increased. Whereby, the internal pressureincrease is avoided.

However, in the structure described in patent document 1, the sidesurface part of the upper header is connected to the vapor pipe.Therefore, the thickness of the upper header has to be at least greaterthan the outer diameter of the vapor pipe. As a result, when the heightof the cooling device is reduced, because the thickness of the upperheader cannot be reduced, the length of the flat pipe has to beshortened. Accordingly, a problem in which the cooling performancedecreases occurs.

In contrast, the upper header 5 of the cooling device 10 according tothis exemplary embodiment is connected to the vapor pipe 3 at theconnection port 20 disposed in the lower surface part of an extensionheader unit 5 b. In other words, because the side surface part of theupper header 5 is not connected to the vapor pipe 3, the thickness inthe vertical direction can be reduced.

In the cooling device 10, it is not necessary to increase the thicknessof the upper header 5 in order to avoid the decrease in coolingperformance due to rapid increase of the volume of the refrigerant whenthe phase of the refrigerant is changed from the liquid phase to the gasphase. As a result, the height of the cooling device 10 can be reduced.Namely, by the cooling device 10 according to this exemplary embodiment,the cooling device 10 using the boiling cooling system which has asufficient cooling performance even when the size of the cooling device10 is reduced can be obtained.

In other words, when the mounting height of the cooling device 10 islimited, by reducing the thickness of the upper header 5, the length ofthe heat dissipation flow path 7 can be made long. Therefore, thecooling performance can be further improved.

Further, a pipe having a straight line shape can be used for the vaporpipe 3 which connects the upper part of the evaporation unit 1 and thelower surface part of the upper header 5. Therefore, it is not necessaryto deform the vapor pipe 3 having a large cross-sectional area and thecost for the manufacturing process can be reduced.

Further, because a bending work is not required to produce the vaporpipe 3, the condensing unit 2 can be disposed near the evaporation unit1 and the size of the cooling device 10 can be further reduced.

When the vapor pipe 3 and the liquid pipe 4 have a bilayer structure inwhich an inner layer is a metal layer and an outer layer is a resinlayer, the following effect is obtained. Namely, even when the vapor ofthe refrigerant (gas-phase refrigerant) or the high temperaturerefrigerant flows inside the vapor pipe 3 and the liquid pipe 4, becausethe inner layer is a resin layer, generation of uncondensed gas due toreaction between the refrigerant and the resin layer can be prevented.As a result, the decrease in cooling performance due to the increase ofthe internal pressure inside a cooler caused by the generation of theuncondensed gas can be prevented.

Second Exemplary Embodiment

Next, a second exemplary embodiment will be described in detail withreference to FIG. 2. FIG. 2 is a perspective view of the cooling device10 according to this exemplary embodiment.

Explanation of the Structure

The cooling device 10 according to this exemplary embodiment has astructure in which the cross-sectional area of the upper headerextension portion 5 b is greater than the cross-sectional area of thevapor pipe 3. The cross-sectional area of the upper header extensionportion 5 b is a cross-sectional area perpendicular to a direction fromthe connection port 20 connected to the vapor pipe 3 toward the flowpath header 5 a. This is a difference between the cooling device 10according to the second exemplary embodiment and the cooling device 10according to the first exemplary embodiment. Besides the above-mentioneddifference, the structure and the connection relationship of the coolingdevice 10 according to the second exemplary embodiment are the same asthose of the cooling device 10 according to the first exemplaryembodiment and the cooling device 10 according to the second exemplaryembodiment includes the evaporation unit 1, the condensing unit 2, thevapor pipe 3, and the liquid pipe 4.

The evaporation unit 1 has an enclosed structure and stores therefrigerant therein. In the cooling device 10, the internal pressure iskept equal to a saturated vapor pressure in a state in which the insidethereof is decompressed by a pump or the like. Further, the lowersurface part of the evaporation unit 1 is thermally connected to theheating element when the evaporation unit 1 is used. Therefore, therefrigerant receives the heat generated by the heating element andboils.

The heat dissipation flow path 7 has a shape extending in the verticaldirection. The upper end part of the heat dissipation flow path 7 isconnected to the upper header 5 and the lower end part thereof isconnected to the lower header 6. The vapor pipe 3 connects the upperpart of the evaporation unit 1 and the upper header 5 and conveys thevapor of the refrigerant (gas-phase refrigerant) that is produced byvaporizing the refrigerant in the evaporation unit 1 to the heatdissipation flow path 7 via the upper header. The liquid pipe 4 connectsthe lower header 6 and the lower part of the evaporation unit 1 andconveys the liquefied refrigerant (liquid-phase refrigerant) obtained bycondensing the gas-phase refrigerant in the condensing unit 2 to theevaporation unit 1.

The upper header 5 is composed of the flow path header portion 5 aconnected to the heat dissipation flow path 7 and the upper headerextension portion 5 b located around the flow path header portion 5 a.The lower surface part of the flow path header portion 5 a is connectedto the heat dissipation flow path 7. Further, the connection port 20connected to the vapor pipe 3 is provided in the lower surface part ofthe upper header extension portion 5 b. Namely, the lower surface partof the upper header 5 composed of the flow path header portion 5 a andthe upper header extension portion 5 b is connected to the vapor pipe 3and the heat dissipation flow path 7. The upper header 5 conveys thevapor of the refrigerant (gas-phase refrigerant) that is conveyed by thevapor pipe 3 to the heat dissipation flow path 7.

As shown in FIG. 2, the cooling device 10 according to this exemplaryembodiment has a structure in which a cross-sectional area perpendicularto a direction from the connection port 20 of the upper header extensionportion 5 b toward the flow path header 5 a is greater than thecross-sectional area perpendicular to a vertical direction of the vaporpipe 3. Further, the arrangement of the vapor pipe 3 is not limited inparticular.

Explanation of the Action and Effect

Next, the action and effect of this exemplary embodiment will bedescribed.

The refrigerant provided in the evaporation unit 1 receives the heatgenerated by the heating element and boils. The vapor of the refrigerantthat is generated when the refrigerant boils is conveyed to the upperheader 5 through the vapor pipe 3 by buoyancy due to the densitydifference between the gas and the liquid.

The vapor of the refrigerant (gas-phase refrigerant) that is conveyed tothe upper header 5 flows in the heat dissipation flow path 7 andwhereby, the heat exchange with the outside air is performed. When theheat dissipation flow path 7 is cooled, the vapor of the refrigerant(gas-phase refrigerant) that flows inside the heat dissipation flow path7 is cooled and condensed to the liquid. The liquefied refrigerant(liquid-phase refrigerant) falls to the lower part of the heatdissipation flow path 7 by the gravity and flows back to the evaporationunit 1. The refrigerant boils by the heat generated by the heatingelement in the evaporation unit 1 again and the cooling cycle isrepeated.

In other words, the refrigerant provided inside the evaporation unit 1changes from the liquid to the gas by the heat generated by the heatingelement and when it flows in the heat dissipation flow path 7, it iscooled and the gas is condensed to the liquid again. Namely, the phaseof the refrigerant is repeatedly changed from the liquid phase to thegas phase and from the gas phase to the liquid phase and whereby, theheat generated by the heating element is dissipated through the heatdissipation flow path 7.

The cross-sectional area perpendicular to a direction from theconnection port 20 of the upper header extension portion 5 b accordingto this exemplary embodiment toward the flow path header 5 a is greaterthan the cross-sectional area perpendicular to a vertical direction ofthe vapor pipe 3. By using the above-mentioned structure, the coolingdevice 10 can reduce a pressure loss of the vapor of the refrigerant(gas-phase refrigerant) and improve the cooling performance in theevaporation unit 1.

Explanation will be made in detail by using FIG. 3. The vapor of therefrigerant (gas-phase refrigerant) generated when the refrigerant boilsby the heat of the heating element in the evaporation unit 1 flows in avertical upper direction through the vapor pipe 3. The vapor pipe 3 isconnected to the lower surface part of the upper header extensionportion 5 b. Therefore, a flow direction of the vapor of the refrigerant(gas-phase refrigerant) changes from the vertical upper direction to ahorizontal direction at a connection point between the vapor pipe 3 andthe upper header extension portion 5 b.

Here, it is assumed that the cross-sectional area perpendicular to adirection from the connection port 20 of the upper header extensionportion 5 b toward the flow path header 5 a is equal to or smaller thanthe cross-sectional area perpendicular to a vertical direction of thevapor pipe 3. In this case, it is estimated that the vapor of therefrigerant (gas-phase refrigerant) flows in the upper header extensionportion 5 b at a speed that is equal to or faster than a speed at whichit flows in the vertical upper direction in the vapor pipe 3.

However, the flow direction of the vapor of the refrigerant (gas-phaserefrigerant) is changed from the vertical upper direction to thehorizontal direction at the connection point between the vapor pipe 3and the upper header extension portion 5 b. Therefore, when the flowdirection of the vapor of the refrigerant (gas-phase refrigerant) ischanged while keeping the speed of flow constant, a pressure loss occursat the connection point between the vapor pipe 3 and the upper headerextension portion 5 b and the cooling performance decreases.

In contrast, the cooling device 10 according to this exemplaryembodiment has a structure in which the cross-sectional areaperpendicular to a direction from the connection port 20 of the upperheader extension portion 5 b toward the flow path header 5 a is greaterthan the cross-sectional area perpendicular to a vertical direction ofthe vapor pipe 3.

Because the cooling device 10 according to this exemplary embodiment hasthe above-mentioned structure, the speed of flow of the vapor of therefrigerant (gas-phase refrigerant) that flows in the upper headerextension portion 5 b decreases. Therefore, the pressure loss thatoccurs when the flow direction of the vapor of the refrigerant(gas-phase refrigerant) is changed from the vertical upper direction inwhich the vapor of the refrigerant flows in the vapor pipe 3 to thehorizontal direction in which it flows in the upper header extensionportion 5 b at a connection point between the vapor pipe 3 and the upperheader extension portion 5 b can be reduced. As a result, the coolingperformance of the cooling device 10 can be further improved.

Namely, when the flow direction of the vapor of the refrigerant(gas-phase refrigerant) is changed from the vertical upper direction tothe horizontal direction at the connection point between the vapor pipe3 and the upper header extension portion 5 b, the flow speed is reduced.Therefore, occurrence of the pressure loss can be prevented.

When the width of the upper header extension portion 5 b in thedirection from the connection port 20 toward the flow path header 5 aand the width thereof in the vertical direction are at least greaterthan the outer diameter of the vapor pipe 3, the widths of the upperheader extension portion 5 b in those directions may be smaller than thewidths of the flow path header portion in those directions,respectively.

Further, the width of the upper header extension portion 5 b in thedirection from the connection port 20 toward the flow path header 5 aand the width of the upper header extension portion 5 b in the verticaldirection are approximately equal to the widths of the flow path headerportion 5 a in those directions, respectively, the upper headerextension portion 5 b and the flow path header portion 5 a can bemanufactured in the same process. Therefore, the manufacturing cost canbe suppressed.

It is desirable that the length of the upper header extension portion 5b in the direction from the connection port 20 toward the flow pathheader 5 a is smaller than the length of the vapor pipe 3 in thevertical direction.

In the vapor pipe 3 extending in the vertical direction, the refrigerantvapor (gas-phase refrigerant) receives a buoyancy force continuously. Onthe other hand, in the upper header extension portion 5 b, therefrigerant vapor moves in the horizontal direction. Therefore, it doesnot receive the buoyancy force and loses the energy by friction with thewall continuously.

Therefore, when the length of the upper header extension portion 5 b inthe direction from the connection port 20 toward the flow path header 5a is smaller than the length of the vapor pipe 3 in the verticaldirection, the influence on the cooling performance is small.

Third Exemplary Embodiment

Next, a third exemplary embodiment will be described in detail by usingFIGS. 4 and 5. FIGS. 4 and 5 are perspective views showing a structureof the cooling device 10 according to this exemplary embodiment.

Explanation of the Structure

The condensing unit 2 of the cooling device 10 according to thisexemplary embodiment is composed of a plurality of the heat dissipationflow paths 7 and the vapor pipe 3 is disposed in a directionperpendicular to the direction in which a plurality of the heatdissipation flow paths 7 are disposed in parallel. This is a differencebetween the cooling device 10 according to the third exemplaryembodiment and the cooling device 10 according to the first exemplaryembodiment. Besides the above-mentioned difference, the structure andthe connection relationship of the cooling device 10 according to thethird exemplary embodiment are the same as those of the cooling device10 according to the first exemplary embodiment and the cooling device 10according to the third exemplary embodiment includes the evaporationunit 1, the condensing unit 2, the vapor pipe 3, and the liquid pipe 4.

The evaporation unit 1 has an enclosed structure and stores therefrigerant therein. In the cooling device 10, the air is exhausted by apump or the like and the internal pressure is equal to the saturatedvapor pressure of the refrigerant. Further, the evaporation unit 1 isset so that the lower surface part of the evaporation unit 1 isthermally connected to the heating element and used. The refrigerantreceives the heat generated by the heating element and boils.

The condensing unit 2 according to this exemplary embodiment is composedof a plurality of the heat dissipation flow paths 7 and a heatdissipation fin 8 is provided in between a plurality of the heatdissipation flow paths 7. The heat dissipation fin 8 is disposed inbetween the adjacent heat dissipation flow paths 7 and thermallyconnected to the adjacent heat dissipation flow paths 7.

Further, the heat dissipation flow path 7 has a shape extending in thevertical direction. The upper end part of the heat dissipation flow path7 is connected to the upper header 5 and the lower end part thereof isconnected to the lower header 6. The vapor pipe 3 connects the upperpart of the evaporation unit 1 and the upper header 5 and conveys thevapor of the refrigerant (gas-phase refrigerant) that is produced byvaporizing the refrigerant in the evaporation unit 1 to the heatdissipation flow path 7 via the upper header 5. The liquid pipe 4connects the lower header 6 and the lower part of the evaporation unit 1and conveys the liquefied refrigerant (liquid-phase refrigerant)obtained by condensing the gas-phase refrigerant in the condensing unit2 to the evaporation unit 1.

The upper header 5 is composed of the flow path header portion 5 aconnected to the heat dissipation flow path 7 and the upper headerextension portion 5 b located around the flow path header portion 5 a.The lower surface part of the flow path header portion 5 a is connectedto the heat dissipation flow path 7. Further, the connection port 20connected to the vapor pipe 3 is provided in the lower surface part ofthe upper header extension portion 5 b. Namely, the lower surface partof the upper header 5 composed of the flow path header portion 5 a andthe upper header extension portion 5 b is connected to the vapor pipe 3and the heat dissipation flow path 7. The upper header 5 conveys thevapor of the refrigerant (gas-phase refrigerant) that is conveyedthrough the vapor pipe 3 to the heat dissipation flow path 7.

In the condensing unit 2 according to this exemplary embodiment, aplurality of the heat dissipation flow paths 7 are provided. As shown inFIG. 4, a plurality of the heat dissipation flow paths 7 are disposed inparallel and connected to the flow path header 5 a.

The vapor pipe 3 is disposed in a direction perpendicular to thedirection in which a plurality of the heat dissipation flow paths 7 aredisposed in parallel. In other words, the vapor pipe 3 is disposed at aposition facing the condensing unit 2. When a plurality of heatingelements exist or when a large amount of heat is generated by theheating element, as shown in FIG. 5, a plurality of the evaporationunits 1 may be connected to the upper header extension portion 5 b byusing a plurality of the vapor pipes 3.

Explanation of the Action and Effect

Next, the action and effect of this exemplary embodiment will bedescribed.

The refrigerant provided in the evaporation unit 1 receives the heatgenerated by the heating element and boils. The vapor of the refrigerant(gas-phase refrigerant) that is generated when the refrigerant boils isconveyed to the upper header 5 through the vapor pipe 3 by buoyancy dueto the density difference between the gas and the liquid.

The vapor of the refrigerant (gas-phase refrigerant) that is conveyed tothe upper header 5 flows in the heat dissipation flow path 7 andwhereby, the heat exchange with the outside air is performed. When theheat dissipation flow path 7 is cooled, the vapor of the refrigerant(gas-phase refrigerant) that flows inside the heat dissipation flow path7 is cooled and condensed to the liquid. The liquefied refrigerant(liquid-phase refrigerant) falls to the lower part of the heatdissipation flow path 7 by the gravity and flows back to the evaporationunit 1. The refrigerant boils by the heat generated by the heatingelement in the evaporation unit 1 again and the cooling cycle isrepeated.

In other words, the refrigerant provided inside the evaporation unit 1changes from the liquid to the gas by the heat generated by the heatingelement and when it flows in the heat dissipation flow path 7, it iscooled and the gas is condensed to the liquid again. Namely, the phaseof the refrigerant is repeatedly changed from the liquid phase to thegas phase and from the gas phase to the liquid phase and whereby, theheat generated by the heating element is dissipated through the heatdissipation flow path 7.

The condensing unit 2 according to this exemplary embodiment includes aplurality of the heat dissipation flow paths 7. The heat dissipation fin8 is disposed in between a plurality of the adjacent heat dissipationflow paths 7. By providing the heat dissipation fin 8, a surface area ofthe heat dissipation flow path 7 is increased. Therefore, the coolingperformance of the refrigerant can be improved because the heat exchangewith outside air is promoted.

Further, when a plurality of the heat dissipation flow paths 7 aredisposed in parallel, an area required to mount the cooling device 10 isat least equal to an area corresponding to a sum of the widths of aplurality of the heat dissipation flow paths 7. The vapor pipe 3according to this exemplary embodiment is disposed in a directionperpendicular to the direction in which a plurality of the heatdissipation flow paths 7 are disposed in parallel.

By using the above-mentioned structure, even when the vapor pipe 3 isdisposed, it is not necessary to further increase the width of the facefacing the vapor pipe 3 of the cooling device 10. Therefore, the size ofthe cooling device 10 can be reduced. Further, as shown in FIG. 5, bydisposing a plurality of the vapor pipes 3 in a direction perpendicularto the direction in which a plurality of the heat dissipation flow paths7 are disposed in parallel, the cooling performance can be improvedwithout increasing the width of the area required to mount the coolingdevice 10.

Further, as shown in FIG. 2, in a structure in which the vapor pipe 3 isdisposed in a direction perpendicular to the direction in which aplurality of the heat dissipation flow paths 7 are disposed in parallel,the upper header extension portion 5 b may have a shape in which theupper header extension portion 5 b is extended in the direction towardthe vapor pipe 3 so as to form a roof that overhangs the vapor pipe 3.

By using the above-mentioned structure like the second exemplaryembodiment, a structure in which the cross-sectional area perpendicularto the direction from the connection port 20 of the upper headerextension portion 5 b toward the flow path header 5 a is greater thanthe cross-sectional area perpendicular to the vertical direction of thevapor pipe 3 is used. Whereby, the pressure loss of the vapor of therefrigerant (gas-phase refrigerant) can be reduced and the coolingperformance in the evaporation unit 1 can be improved.

The cooling device 10 according to this exemplary embodiment can havenot only the above-mentioned action and effect but also a duct effect.When described in detail, the upper header extension portion 5 b isextended in the direction toward the vapor pipe 3 so as to form anoverhanging roof. Whereby, the upper header extension portion 5 b canprevent the wind for cooling the heat dissipation flow path 7 fromflowing upward and control the flow direction of the wind. As a result,the heat dissipation flow path 7 can be cooled by the cooling windflowing in the vertical direction. Therefore, the pressure loss of thecooling wind can be reduced and the efficient cooling can be realized.

Fourth Exemplary Embodiment

Next, a fourth exemplary embodiment will be described in detail withreference to FIG. 6. FIG. 6 is a perspective view of the cooling device10 according to this exemplary embodiment.

Explanation of the Structure

The condensing unit 2 of the cooling device 10 according to thisexemplary embodiment has a structure in which a plurality of the heatdissipation flow paths 7 are disposed in parallel. The vapor pipe 3 isdisposed in line approximately parallel to the direction in which aplurality of the heat dissipation flow paths 7 are disposed in parallel.This is a difference between the cooling device 10 according to thefourth exemplary embodiment and the cooling device 10 according to thefirst exemplary embodiment. Besides the above-mentioned difference, thestructure and the connection relationship of the cooling device 10according to the fourth exemplary embodiment are the same as those ofthe cooling device 10 according to the first exemplary embodiment andthe cooling device 10 according to the fourth exemplary embodimentincludes the evaporation unit 1, the condensing unit 2, the vapor pipe3, and the liquid pipe 4.

The evaporation unit 1 has an enclosed structure and stores therefrigerant therein. In the cooling device 10, the air is exhausted by apump or the like and the internal pressure is equal to the saturatedvapor pressure of the refrigerant. Further, the evaporation unit 1 isset so that the lower surface part of the evaporation unit 1 isthermally connected to the heating element and used. The refrigerantreceives heat generated by the heating element and boils.

The condensing unit 2 according to this exemplary embodiment is composedof a plurality of the heat dissipation flow paths 7 and the heatdissipation fin 8 is provided in between a plurality of the heatdissipation flow paths 7. The heat dissipation fin 8 is disposed inbetween the adjacent heat dissipation flow paths 7 and thermallyconnected to the adjacent heat dissipation flow paths 7.

Further, the heat dissipation flow path 7 has a shape extending in thevertical direction. The upper end part of the heat dissipation flow path7 is connected to the upper header 5 and the lower end part thereof isconnected to the lower header 6. The vapor pipe 3 connects the upperpart of the evaporation unit 1 and the upper header 5 and conveys thevapor of the refrigerant (gas-phase refrigerant) that is produced byvaporizing the refrigerant in the evaporation unit 1 to the heatdissipation flow path 7 via the upper header 5. The liquid pipe 4connects the lower header 6 and the lower part of the evaporation unit 1and conveys the liquefied refrigerant (liquid-phase refrigerant)obtained by condensing the gas-phase refrigerant in the condensing unit2 to the evaporation unit 1.

The upper header 5 is composed of the flow path header portion 5 aconnected to the heat dissipation flow path 7 and the upper headerextension portion 5 b located around the flow path header portion 5 a.The lower surface part of the flow path header portion 5 a is connectedto the heat dissipation flow path 7. Further, the connection port 20connected to the vapor pipe 3 is provided in the lower surface part ofthe upper header extension portion 5 b. Namely, the lower surface partof the upper header 5 composed of the flow path header portion 5 a andthe upper header extension portion 5 b is connected to the vapor pipe 3and the heat dissipation flow path 7. The upper header 5 conveys thevapor of the refrigerant (gas-phase refrigerant) that is conveyedthrough the vapor pipe 3 to the heat dissipation flow path 7.

As shown in FIG. 6, in the cooling device 10 according to this exemplaryembodiment, a plurality of the heat dissipation flow paths 7 provided inthe condensing unit 2 are disposed in parallel. The vapor pipe 3 isdisposed in line approximately parallel to the direction in which aplurality of the heat dissipation flow paths 7 are disposed in paralleland connected to the upper header extension portion 5 b. In other words,the vapor pipe 3 is disposed on an extension line in a direction inwhich a plurality of the heat dissipation flow paths 7 are disposed inparallel.

Explanation of the Action and Effect

Next, the action and effect of this exemplary embodiment will bedescribed.

The refrigerant provided in the evaporation unit 1 receives the heatgenerated by the heating element and boils. The vapor of the refrigerant(gas-phase refrigerant) that is generated when the refrigerant boils isconveyed to the upper header 5 through the vapor pipe 3 by buoyancy dueto the density difference between the gas and the liquid.

The vapor of the refrigerant (gas-phase refrigerant) that is conveyed tothe upper header 5 flows in the heat dissipation flow path 7 andwhereby, the heat exchange with the outside air is performed. When theheat dissipation flow path 7 is cooled, the vapor of the refrigerant(gas-phase refrigerant) that flows inside the heat dissipation flow path7 is cooled and condensed to the liquid. The liquefied refrigerant(liquid-phase refrigerant) falls to the lower part of the heatdissipation flow path 7 by the gravity and flows back to the evaporationunit 1. The refrigerant boils by the heat generated by the heatingelement in the evaporation unit 1 again and the cooling cycle isrepeated.

In other words, the refrigerant provided inside the evaporation unit 1changes from the liquid to the gas by the heat generated by the heatingelement and when it flows in the heat dissipation flow path 7, it iscooled and the gas is condensed to the liquid again. Namely, the phaseof the refrigerant is repeatedly changed from the liquid phase to thegas phase and from the gas phase to the liquid phase and whereby, theheat generated by the heating element is dissipated through the heatdissipation flow path 7.

The condensing unit 2 according to this exemplary embodiment includes aplurality of the heat dissipation flow paths 7. The heat dissipation fin8 is disposed in between a plurality of the adjacent heat dissipationflow paths 7. By providing the heat dissipation fin 8, a surface area ofthe heat dissipation flow path 7 is increased. Therefore, the coolingperformance of the refrigerant can be improved because the heat exchangewith outside air is promoted.

As shown in FIG. 6, the vapor pipe 3 according to this exemplaryembodiment is disposed in line approximately parallel to the directionin which a plurality of the heat dissipation flow paths 7 provided inthe condensing unit 2 are disposed in parallel. In other words, thevapor pipe 3 is disposed on an extension line in a direction in which aplurality of the heat dissipation flow paths 7 are disposed in parallel.

Therefore, because the flow of the cooling wind flowing in the directionperpendicular to the direction in which a plurality of the heatdissipation flow paths 7 are disposed in parallel is not disturbed bythe vapor pipe 3, the heat dissipation flow path 7 can be cooledefficiently. As a result, the cooling efficiency of the cooling device10 can be further improved.

This application claims priority from Japanese Patent Application No.2012-000038 filed on Jan. 4, 2012, the disclosure of which is herebyincorporated by reference in its entirety.

The invention of the present application has been described above withreference to the exemplary embodiment. However, the invention of thepresent application is not limited to the above mentioned exemplaryembodiment. Various changes in the configuration or details of theinvention of the present application that can be understood by thoseskilled in the art can be made without departing from the scope of theinvention of the present application.

DESCRIPTION OF SYMBOL

-   1 evaporation unit-   2 condensing unit-   3 vapor pipe-   4 liquid pipe-   5 upper header-   5 a flow path header portion-   5 b upper header extension portion-   6 lower header-   7 heat dissipation flow path-   8 heat dissipation fin-   10 cooling device-   20 connection port

1. A cooling device comprising: an evaporation unit which storesrefrigerant; a condensing unit which condenses a gas-phase refrigerantproduced by vaporizing the refrigerant in the evaporation unit to aliquid and dissipates heat; a vapor pipe which conveys the gas-phaserefrigerant to the condensing unit; and a liquid pipe which conveys aliquid-phase refrigerant obtained by condensing the gas-phaserefrigerant in the condensing unit to the evaporation unit, wherein thecondensing unit includes a heat dissipation flow path, an upper headerwhich connects the vapor pipe and the heat dissipation flow path, and alower header which connects the heat dissipation flow path and theliquid pipe, the upper header includes a flow path header portionconnected to the heat dissipation flow path and an upper headerextension portion located around the flow path header portion, and theupper header extension portion has a connection port connected to thevapor pipe in a face to which the heat dissipation flow path isconnected.
 2. The cooling device described in claim 1, wherein a widthof the upper header extension portion in a direction from the connectionport toward the flow path header and a width thereof in a verticaldirection are approximately equal to a width of the flow path headerportion in a direction from the connection port toward the flow pathheader and a width thereof in a vertical direction, respectively.
 3. Thecooling device described in claim 1, wherein a width of the upper headerextension portion in a direction from the connection port toward theflow path header and a width thereof in the vertical direction aresmaller than a width of the flow path header portion in a direction fromthe connection port toward the flow path header and a width thereof inthe vertical direction, respectively.
 4. The cooling device described inclaim 1, wherein a cross-sectional area of the upper header extensionportion in the direction from the connection port toward the flow pathheader and a cross-sectional area thereof in the vertical direction aregreater than the cross-sectional area of the vapor pipe.
 5. The coolingdevice described in claim 1, wherein a length of the upper headerextension portion in the direction from the connection port toward theflow path header is smaller than the length of the vapor pipe in thevertical direction.
 6. The cooling device described in claim 1, whereinthe cooling device includes a plurality of the vapor pipes and theevaporation unit is connected to the upper header by a plurality of thevapor pipes.
 7. The cooling device described in claim 1, wherein thecondensing unit is composed of a plurality of the heat dissipation flowpaths and the vapor pipe is disposed in a direction perpendicular to adirection in which a plurality of the heat dissipation flow paths aredisposed in parallel.
 8. The cooling device described in claim 1,wherein the condensing unit is composed of a plurality of the heatdissipation flow paths and the vapor pipe is disposed in lineapproximately parallel to the direction in which a plurality of the heatdissipation flow paths are disposed in parallel.
 9. The cooling devicedescribed in claim 1, wherein the vapor pipe is extended in a straightline shape in a vertical direction.
 10. The cooling device described inclaim 1, wherein the vapor pipe connects an upper part of theevaporation unit and a lower surface part of the upper header and theliquid pipe connects a side surface part of the evaporation unit and thelower header.
 11. The cooling device described in claim 1, wherein thecooling device includes a plurality of the heat dissipation flow paths,a heat dissipation fin is disposed in between a plurality of theadjacent heat dissipation flow paths, and the heat dissipation fin isthermally connected to the heat dissipation flow path.
 12. The coolingdevice described in claim 1, wherein one of the vapor pipe and theliquid pipe has a structure in which an inner layer is a metal layer andan outer layer is a resin layer.